Mold structure for dielectric heating



2 Sheets-Sheet l G. E. GARD MOLD STRUCTURE FOR DIELECTRIC HEATING Dec. 22, 1953 Filed June 25, 1951 INVENTOR GEORGE E- GARD Maw ATTORNEY Dec. 22, 1953 G. E. GARD 2,663,790

MOLD STRUCTURE FOR DIELECTRIC HEATING I IN 42\E l 3:: :J mu :3: i L H as 7 l .5 1 ,Hi c B [IA II I H W E E INVENTOR A x i v GEORGE EGARD 36 l I l l I I l t 4| 40 Adam vh ATTORNEY ueferring to Figure 1, there is shown a mold of the type disclosed and claimed in the copending application of Louis H. Lockwood, Serial No. 200,560, filed December 13, 1950 now Patent No. 2,625,710, and entitled Mold Structure. The mold includes side wall members 2 and 3 and end wall members 4 and 5. Each of the side wall members 2 and 3 is made up of a plurality of pieces of dielectric material such as pieces 6 of hardwood disposed as panels. The end wall members are similarly fabricated from pieces of dielectric material 1. Each of the wall members includes an upper frame member 8, as shown in Figure 2, and a lower frame member 9. Pockets iii are provided between flange i I and peripheral conductor I2. The dielectric panels 6 and l are received within the pockets ofv the frames, and the parts are joined by pins l3 which extend through the flanges, the dielectric panels, and the peripheral conductors. The wall members are mechanically fastened together with ma.- chine screws it and i5, as indicated in Figure l.

The mold is provided with an upper electrode l6 and a lower electrode ll, the upper electrode being held in position by locking keys 18.

The structure shown in Figures 1 and '2 is more fully described and illustrated in the Lockwood application referred to above.

It will be observed by reference to Figure 2 that there is provided on each of the frame members a projecting web l9 which constitutes a discharge conductor. This discharge conductor is spaced outwardly from the peripheral conductors l2; and when the wall members are joined together, as shown in Figure 1, the discharge conductors it will extend around substantially the entire periphery of the mold wall, except for the limited areas where the fastenings Ill and it are received within openings in the frame members, as shown at the corners in Figure 1.

In this structure the distance between the electrodes l8 and l'i has been indicated by the letter A, the distance between the peripheral conductors by the letter B, and the distance between the discharge conductors by the letter C. The distance A is greater than distance E, and distance C is less than distance B. Thus when the electrodes i and i? are connected to a source of highfrequency alternating electric current for the dielectric heating of the mass disposed within the mold, a more intensive field of force will be established in the dielectric mold walls than in the mass due tothe fact that the peripheral conductors are spaced from one another a distance B which is less than the spacing A between electrodes. This action is fully set forth in Scott Patent 2,526,697. The peripheral conductors are disposed in contact with the mold walls, but danger from arcing between the peripheral conductors at the mold walls is obviated by the provision of the discharge conductors which are spaced outwardly from the peripheral conductors and from the mold walls and are spaced from one another a distance C which is less than the distance B between the peripheral conductors and the distance A between the electrodes IE and 17.

It is preferred to have .the terminal edges 2| of the discharge conductors rounded so as to eliminate any points or sharp projections which would serve to increase the voltage gradient and foster arcing.

Figure 3 shows a modified structure embodying the present invention in which there are provided mold walls 22 which may be made of hardwood impregnated with ceresin wax, similar to the panels 5 and 1. Frame members 23 and 24 are provided, each of which includes a flange 25, a peripheral conductor 26, and a reinforcing web 21 disposed outwardly from the peripheral conductor 26. The wooden wall members 22 are received Within pockets 28 provided in the frame members and defined by the flanges 25 and the peripheral conductors 25. Discharge conductors 29 are provided which in the embodiment illustrated are in the form of hollow copper tubing electrically connected to the peripheral conductor 26 by supporting brackets 3G which are welded to the peripheral conductor 26 and to the flanges 27. The discharge conductors are welded or brazed to the brackets 3d as indicated at 3! in Figure 3. In this embodiment electrodes 32 and 33 are provided which are electrically connected to the frame members 23 and 2e, and the spacing between these electrodes indicated as the distance A is greater than the spacing between the peripheral conductors indicated by the letter B, and the spacing of the discharge conductors indicated by the letter C is less than the spacing between the peripheral conductors. The principle of operation of this modification is the same as the embodiment shown in Figures 1 and 2. This structure, however, permits the provision of discharge conductors extending around the entire periphery of the mold; whereas, with the STQUC? ture of Figures 1 and 2, the conductors are cut back at the corners to permit fastening together of the frame members.

Figure 4 shows a further modification of the invention in which the mold is of generally hollow cylindrical shape to provide for the melding of cylindrical bodies of cork composition, for instance. The mold wall 3% may be formed of impregnated hardwood as in the other embodiments, and the frame members 35 and 35 may be integrally cast to provide peripheral conductors 3! and discharge conductors 38. Electrodes 39 and 4B are provided, the lower electrode til being held in position by a projecting shoulder ll provided on the lower frame member and the upper electrode being held in position against upward movement by locking key :32 passing through the frame member 55 and the electrode 39. In this embodiment of the invention, the distance A between the electrodes is more than the distance B between the peripheral conductors 31, and the distance C between the discharge conductors 38 is less than the distance between the peripheral conductors. The discharge conductor and the peripheral conductor being integrally formed are electrically connected, and the upper and lower electrodes are connected to their respective frame members by interengagenient therewith and by the lacking key 62. In this embodiment of the invention, as in the embodiment of Figure 3, the discharge conductors 33 extend around the entire perimeter of the mold without interruption, and any arcing which may be occasioned will occur between the discharge conductors rather than between the peripheral corliiiuctors which lie in engagement with the mold wa Preferred practice is to make the frame members as iron castings with integral webs constituting the peripheral conductors and discharge conductors, for by so doin a rigid structure is fabricated. This is particularly desirable where the mass to be treated is confined within t mold under substantial pressure. The invention, however, is not limited to this type of structure, for e p lpheral conductors and the discharge conductors may be formed separately from the frame members, if such be provided, with the upper discharge conductor and the upper peripheral conductor being connected to the upper electrode and the lower electrode being electrically connected to its lower peripheral conductor and discharge conductor.

I claim:

1. In a mold for the dielectric heating of materials, the combination of a mold wall of dielectric material; metal frames secured to the upper and lower edges of the mold Wall and embracing the same on the outer surface thereof as upper and lower peripheral conductors disposed around the outer perimeter of the mold wall and spaced from one another; upper and lower discharge conductors disposed around the outer perimeter of the mold wall, spaced outwardly from the mold wall, electrically connected to said upper and lower peripheral conductors, respectively, and spaced from one another a distance less than the distance between said peripheral conductors; and upper and lower electrodes received within said mold wall, electrically connected to said upper and lower metal frames, respectively, and spaced from one another a distance greater than the distance between said peripheral conductors.

2. In a mold for the dielectric heating of materials, the combination of mold walls of dielectric material; multiwebbed metal frames secured to the upper and lower edges of the mold walls, a web on each of the frames embracing the mold Walls on the outer surface thereof as upper and lower peripheral conductors disposed around the outer perimeter of the mold walls and spaced from one another, a second associated web on each of the frames spaced outwardly from the mold walls, disposed around the outer perimeter of the mold walls as upper and lower discharge conductors, and spaced from one another a distance less than the distance between said peripheral conductors, each peripheral conductor and its associated discharge conductor being electrically connected; and upper and lower electrodes received within said mold walls, electrically connected to said upper and lower multiwebbed metal frames, respectively, and spaced from one another a distance greater than the distance between said peripheral conductors.

3. In a mold for the dielectric heating of materials, the combination of mold walls of dielectric material disposd as a parallelpiped open at the top and bottom; multiwebbed metal frames secured to the upper and lower edges of the mold walls, a pair of spaced webs on each of the frames receiving the mold walls therebetween, with one of said webs of each of said frames embracing the mold walls on the outer surface thereof as upper and lower peripheral conductors disposed around the outer perimeter of the mold and spaced from one another, the other of said pair of webs embracing the mold walls on the inner surface thereof and spaced from one another a distance greater than the distance between the peripheral conductors, a third associated web on each of the frames spaced outwardlyfrom the mold walls, disposed around the outer perimeter of the mold walls as upper and lower discharge conductors, and spaced from one another a distance less than the distance between said peripheral conductors, each peripheral conductor and its associated discharge conductor being electrically connected; and upper and lower electrodes received within the open top and bottom of said mold walls, electrically connected to said upper and lower multiwebbed metal frames, respectively, and spaced from one another a distance greater than the distance between said peripheral conductors.

4. In a mold for the dielectric heating of materials, the combination of a mold wall of dielectric material; upper and lower peripheral conductors disposed around the outer perimeter of the mold wall and spaced from one another; upper and lower discharge conductors disposed around the outer perimeter of the mold wall, spaced outwardly from the peripheral conductors, electrically connected to the upper and lower peripheral conductors, respectively, and spaced from one another a distance less than the distance between said peripheral conductors; and upper and lower electrodes electrically connected to said upper and lower peripheral conductors, respectively, and spaced from one another a distance greater than the distance between said peripheral conductors.

5. In a mold for the dielectric heatin of materials, the combination of a mold wall of dielectric material; upper and lower peripheral conductors disposed around the outer perimeter of the mold wall and spaced from one another; associated upper and lower discharge conductors of rounded configuration disposed around the outer perimeter of the mold wall, spaced outwardly from the respective associated peripheral conductors, and spaced from one another a distance less than the distance between said peripheral conductors; electrically conductive metal brackets electrically connected to said upper and lower peripheral conductors and said upper and lower discharge conductors, respectively, and securing said discharge conductors in spaced relationship with respect to said respective associated peripheral conductors; and upper and lower electrodes electrically connected to said upper and lower peripheral conductors, respectively, and spaced from one another a distance greater than the distance between said peripheral conductors.

6. In a mold for the dielectric heating of materials, the combination of a hollow cylindrical mold wall of dielectric material; upper and lower annular peripheral conductors disposed around the outer perimeter of the mold wall and spaced from one another; upper and lower annular discharge conductors disposed around the outer perimeter of the mold wall, spaced outwardly from the mold wall, electrically connected to said upper and lower annular peripheral conductors, respectively, and spaced from one another a distance less than the distance between said peripheral conductors; and upper and lower electrodes received within said mold wall, electrically connected to said upper and lower annular peripheral conductors, respectively, and spaced from one another a distance greater than the distance between said peripheral conductors.

GEORGE E. GARD.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,521,797 Klingaman Sept. 12, 1950 2,521,808 Taylor Sept. 12, 1950 2,526,697 Scott, Jr Oct. 24, 1950 FOREIGN PATENTS Number Country Date 619,398 Great Britain Mar. 9, 1949 

